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Human Biology Sylvia S. Mader Michael Windelspecht Chapter 7 Lymphatic System and Immunity Lecture Outline Part 3 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 7.4 Adaptive Immune Defenses What do the specific defenses include? • Third line of defense – Helps protect us against ________ pathogens when nonspecific defenses fail – Helps protect us against cancer – Depends on the action of B and T cells (remember that these are lymphocytes) 2 7.4 Adaptive Immune Defenses What are the types of B and T cells? • B cells produce plasma cells and memory cells. – ___________ produce specific antibodies. – ___________ are ready to produce antibodies in the future. 3 7.4 Adaptive Immune Defenses What are the types of B and T cells? • T cells regulate immune response; produce various types of T cells. – Cytotoxic T (Tc) cells kill ____________ and _______ cells. – Helper T (TH) cells regulate immunity. – Memory T (Tc and TH) cells are ready to kill in the ________. 4 7.4 Adaptive Immune Defenses What are the types of B and T cells? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. memory B cell B cell antibody Antibodymediated immunity plasma cell BCR APC antigen TCR memory TH cell Adaptive defenses TH cell activated TH cell activated TC cell Cellmediated immunity antigen memory TC cell virus-infected cell TCcell TCR Figure 7.10 Overview of adaptive immune defenses. 5 7.4 Adaptive Immune Defenses What are the characteristics of B cells? • _______________ immunity against pathogens • Produced and mature in bone marrow • Directly _________________ and then undergo clonal selection • Clonal expansion produces antibody-secreting plasma cells as well as memory B cells 6 7.4 Adaptive Immune Defenses Third line of defense: Antibodymediated immunity by B cells • Each B cell has a unique receptor called a BCR that binds a specific antigen. • This binding and cytokines secreted by helper T cells result in clonal expansion in which this B cell makes copies of itself. • Most of the cells produced are ____________ that secrete antibodies . 7 7.4 Adaptive Immune Defenses Third line of defense: Antibodymediated immunity by B cells • Other cells become memory cells which result in long-term immunity. • After an infection has passed, plasma cells undergo ___________ (programmed cell death) leaving memory cells. 8 7.4 Adaptive Immune Defenses Antibody-mediated immunity by B cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. antigen B cell antigens cytokines from T cells B-cell receptor (BCR) Plasma cells Memory B cells a. Activation: When a B cell receptor binds to an antigen activation occurs. b. Clonal expansion – During clonal expansion, cytokines secreted by helper T cells stimulate B cells to clone mostly into plasma cells or memory cells. Apoptosis c. Apoptosis – Apoptosis, or programmed cell death, occurs to plasma cells left in the system after the infection has passed. Figure 7.11 Antibody-mediated immunity, or the clonal selection model for B cells. 9 7.4 Adaptive Immune Defenses Structure of antibodies • The basic unit that composes antibody molecules is a ____________ protein. • The trunk of the Y is a constant region that determines the class of the antibody. • The ends of the arms (Y) are the variable regions where specific antigens bind. 10 7.4 Adaptive Immune Defenses Structure of antibodies Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. antigen-binding sites antigen Antigen binds to binding site. light chain Shape of antigen fits shape of binding site. C C heavy chain C = constant V = variable a. b. Figure 7.12 The structure of an antibody. b: Courtesy Dr. Arthur J. Olson, Scripps Institute 11 7.4 Adaptive Immune Defenses What are the 5 classes of antibodies? 12 7.4 Adaptive Immune Defenses How do we make monoclonal antibodies? • We make monoclonal antibodies (derived from plasma cells that originated from the same B cell) in glassware outside the body (in vitro). • This is done through fusion of plasma cells with myeloma cells that allow them to divide indefinitely. • This fusion results in a cell called a hybridoma. 13 7.4 Adaptive Immune Defenses How do we make monoclonal antibodies? Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. antibody plasmacell antigen hybridomacell cancerous myelomacell monoclonal antibody Figure 7.13 The production of monoclonal antibodies. 14